BOOSTING BIOBASED CONTENT IN PVOH FILMS: COMPARATIVE THERMO-MECHANICAL PERFORMANCE OF LIGNIN AND NANOCELLULOSES AS REINFORCEMENTS

The transition to a circular economy in packaging has become a strategic priority due to increasing regulatory pressure and environmental awareness. The use of bio-based and degradable, and/or recycled materials contributes to the development of sustainable, circular material flows. This has driven research into incorporating renewable components into polymer systems. Poly(vinyl alcohol) (PVOH), a water-soluble synthetic polymer with excellent film-forming properties, is particularly suitable for such enhancements due to its compatibility with natural additives.

In this study, we investigate the thermo-mechanical performance of PVOH films reinforced separately with lignin and nanocelluloses to assess their effectiveness in improving thermo-mechanical properties and increasing overall bio-based content.

PVOH composite films were prepared by solvent casting with varying loadings (5%, 10%, 20%) of lignin and nanocellulose. Hydropol™ PVOH was provided by Aquapack Polymers. Organosolv lignin was extracted from Jartropha Curcas L. seed coats, while enzymatic cellulose nanofibrils were obtained from bleached kraft pulp. Mechanical and thermal properties were evaluated using tensile testing and thermal analysis (DSC, TGA).

Results showed that 5% loading of both reinforcements improved the mechanical strength and thermal stability of PVOH films. Nanocellulose provided greater increase in tensile strength and modulus due to its high aspect ratio and strong hydrogen bonding with the PVOH. In contrast, lignin improved thermal stability while preserving the film’s flexibility, likely due to its aromatic, amorphous structure.

These findings reveal distinct reinforcement mechanisms, highlighting the potential for tailored material design based on specific performance needs. Overall, lignin and nanocellulose are promising sustainable reinforcements for PVOH films, advancing the development of high-performance, bio-based polymer composites.

Acknowledgments

RM is grateful for Grant RYC2021-034380-I funded by MCIN/AEI/10.13039/501100011033 and by European Union “NextGenerationEU”/PRTR. RM and GC also acknowledge funding from Aquapak Polymers.